Internal combustion engines which are used in motor chain saws, cutoff machines and similar hand-held portable tools are usually in the form of two-stroke engines and warm considerably during use. After the engine is turned off, the temperature can continue to rise because the cooling system is also shut down when the engine is turned off; this can cause overpressure because of fuel vaporization to develop in the tank with increased warming thereof. Because of this situation, the disadvantage occurs in practice that the inlet valve opens because of the overpressure so that fuel floods the cylinder and starting difficulties are encountered when one restarts the engine.